1. Field
The present field relates to a real-time location detection system, which uses MEMS and GPS sensors to achieve high location-prediction accuracy while conserving energy.
2. Related Art
Real-time location-detection allows for many location-based applications such as store finding, transit routing, and ads targeting. In outdoor environments, GPS and cell-tower signals are typically used for detecting the location of mobile devices. However, cell-tower signals may not provide highly accurate or precise information about location. and GPS signals may not be available when satellite signals are obstructed, such as when the mobile device is in or near a building. Moreover, receiving and processing GPS signals may consume substantial energy and hence shorten battery duration.
In addition to GPS sensors, some mobile devices are equipped with MEMS (Microelectromechanical Systems) sensors. MEMS sensors are typically very small mechanical devices which are driven by electricity. Various types of MEMS sensors include accelerometers, digital compasses, functional sensors, gyroscopes, and inertial modules. MEMS sensors can provide information about the movement of a mobile device. For example, they provide information about acceleration or the orientation of an object by generating electrical signals that correspond with dynamic forces, such as user movement of the device, or static forces such as gravity that act on the device.
Current technology may use either GPS or cell-tower signals to determine location. However, GPS signal receiving and processing consumes significant power, and cell-tower signals can provide prediction with only about 300-meter accuracy, or 50-meter accuracy at best. To improve accuracy and power consumption, some aircraft employ several GPS antennas to determine location information. However, because of the much smaller size of a mobile device (compared to an aircraft), the multiple-antenna approach may not be possible, because the length of GPS signal phase is longer than a mobile device. Moreover, mobile devices require highly precise location information to be optimally useful and power is limited, because most mobile devices obtain their power from a battery. Furthermore, moving patterns of mobile devices may not be as “smooth” as an aircraft.